Well, my first two thoughts are the ability to generate electrical power independently, and lots and lots of firewood, because I am lucky enough to have a wood stove that heats the whole house.

I am on a well system as far as water, and the pump that draws the water into the house of course runs on electricity, so I would probably have to replace that with one that can draw power from the Powerwalls or other large batteries where power is stored from solar or wind.

I know a lot of people will say ammunition. I am lucky enough to live in an area where I don't anticipate needing that much.

More important, I think, is all the medical concerns. I have a first aide kit, but it occurred to me one day that since I am neither a doctor nor a nurse, I don't really know what to do with most of the supplies in the kit. Apart from taking nursing classes or emergency first aide classes, having a girlfriend who is a doctor or nurse would come in very handy.

Then there is the all important communications gear. I think it is a given that you must have satellite communications gear, since the internet and LTE cannot be relied upon to remain up and running. If you're part of a group, learning to set up a MESH network is a worthwhile investment of your time. Which brings us to batteries and the ability to recharge them. I should also learn how HAM radio works.

Paper maps, since GPS will likely not be available. And mountain bikes, still, I think, the most reliable form of transport, and a stealthy one too.

And books, lots of books. And board games. Boredom, strange as it sounds, could easily become a factor when nothing is working.